Solid or semi-solid ionic materials are useful for preparing, among others, solid electrolytes (e.g., gel electrolytes and dry polymer electrolytes). Improved safety and a wider operating temperature range result from use of solid electrolytes, instead of liquid electrolytes, in lithium-ion batteries, fuel cells, and capacitors.
Ionic liquids, contained in certain ionic materials, have desirable properties, such as negligible vapor pressure, thermal stability and non-flammability, high ionic conductivity, and a wide electrochemical stability window. However, it is difficult to prepare an ionic liquid-containing solid electrolyte that has a high ionic conductivity comparable to a neat ionic liquid.
A variety of structural support substrates, e.g., polymers, colloidal particles, carbon nanotubes, and small organic gelators, have been used to immobilize ionic liquids in solid or semi-solid ionic materials. See Horowitz and Panzer, Journal of Materials Chemistry 2012, 22, 16534-39. Polymer ionic materials have attracted tremendous interest as they can have a high ionic conductivity while existing in a non-liquid phase. See id; and Ogoshi et al., Polymer Journal 2011, 43, 421-24. These materials are typically prepared via self-assembly of block copolymers or via in situ thermally or UV initiated radical polymerization. See Horowitz and Panzer, supra. Nevertheless, polymer ionic materials thus prepared often display low thermal stability and high mechanical stiffness, and their successful preparation remains challenging. See id; and Visentin and Panzer, ACS Applied Materials & Interfaces 2012, 4, 2836-39.
There is a need to develop a thermally stable and mechanically flexible solid or semi-solid ionic material that has high ionic conductivity and can be easily and rapidly prepared at low cost.